Spinobulbar muscular atrophy
| Spinal and bulbar muscular atrophy | |
|---|---|
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| SBMA is inherited in an X-linked recessive pattern. | |
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G12.1 |
| ICD-9-CM | 335.1 |
| OMIM | 313200 |
| DiseasesDB | 7144 |
| eMedicine | article/1172604 |
| MeSH | D055534 |
| Orphanet | 481 |
Spinal and bulbar muscular atrophy (SBMA), also known as spinobulbar muscular atrophy, bulbo-spinal atrophy, X-linked bulbospinal neuropathy (XBSN), X-linked spinal muscular atrophy type 1 (SMAX1), Kennedy's disease (KD), and many other names, is a debilitating neurodegenerative disorder resulting in muscle cramps and progressive weakness due to degeneration of motor neurons in the brain stem and spinal cord.
The condition is associated with mutation of the androgen receptor (AR) gene and is inherited in an X-linked recessive manner. As with many genetic disorders, no cure is known, although research continues. Because of its endocrine manifestations related to the impairment of the AR gene, SBMA can be viewed as a variation of the disorders of the androgen insensitivity syndrome (AIS). It is also related to other neurodegenerative diseases caused by similar mutations, such as Huntington's disease.
This condition is rare with an estimated incidence of 1/40,000 males. Although this condition is not normally fatal eventually 20% of those affected may need a wheelchair.
Individuals with SBMA have muscle cramps and progressive weakness due to degeneration of motor neurons in the brain stem and spinal cord. Ages of onset and severity of manifestations in affected males vary from adolescence to old age, but most commonly develop in middle adult life. The syndrome has neuromuscular and endocrine manifestations.
Early signs often include weakness of tongue and mouth muscles, fasciculations, and gradually increasing weakness of limb muscles with muscle wasting. Neuromuscular management is supportive, and the disease progresses very slowly, but can eventually lead to extreme disability. Further signs and symptoms include:
Muscular
Endocrine
Other
Homozygous females, both of whose X chromosomes have a mutation leading to CAG expansion of the AR gene, have been reported to show only mild symptoms of muscle cramps and twitching. No endocrinopathy has been described.
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